2011 iMac Random Reboots

[xxtsxx702]

Hello,
I have a 2011 iMac that has been having random about once a day. I have swapped to a K2100m (flashed with Nick's VBIOS) to allow Catalina to run and the kernel panics do seem to be related to this.

It will tend to crash once a day, but sometimes it may go 3-4 days without a crash or it may crash 2-3 times a day. It sometimes occurs while playing videos, and sometimes it happens when idle. Other times it will crash when it should have been in sleep. It seems to be completely random.

Basic troubleshooting tests were done below:
-Restarts occur with external display and without
-Occurs in High Sierra, Mojave, and Catalina
-K2100M has been swapped with no change
-NVRAM (restarted as expected from the apple guide, but no settings were reset - don't know if it took) and SMC have been attempted
-Tested all RAM sticks individually and restarted on all of them

I have not yet implemented the OpenCore bootloader that should be possible with this setup.

Setup:
Mid 2011, 21.5 iMac
2600S
K2100M 2GB
16GB DDR3 (removed the 4GB stock)

I have uploaded some logs to Google Drive (I have many more) as it appears macrumors doesn't let you upload .rtf files. Does this appear to be a bad GPU or could something else be the issue?

2011 iMac Crash - Google Drive

drive.google.com

Thank you for the help!

 

[ZenSurfeur]

hi
random reboots generaly caused by ram module ram
how did you test the ram?
then what was the original cpu config?

 

[xxtsxx702]

hi
random reboots generaly caused by ram module ram
how did you test the ram?
then what was the original cpu config?

Thanks for the reply!
For the RAM - I had two sets of RAM (4GB stock and 16GB aftermarket). I tested by removing one set (ran with only the 4GB) and then switching to the other (only the 16GB). It rebooted under both conditiond.

I also ran the AHT 3 times (~6 hours) with all 20GB installed and it found no issues.

The original CPU was the i5-2500S

 

[ZenSurfeur]

This iMac is supposed to only support 8Gb max per ram module, maybe this is the cause

I have 4 x 8Gb modules and the iMac wokrs like a charm
[automerge]1586370777[/automerge]
Can you gimme both the specs of the modules?

 

[xxtsxx702]

This iMac is supposed to only support 8Gb max per ram module, maybe this is the cause

I have 4 x 8Gb modules and the iMac wokrs like a charm
[automerge]1586370777[/automerge]
Can you gimme both the specs of the modules?

I probably was not clear enough on that - I have 2x8GB sticks giving 16GB total, not 1x16GB stick.

They are the OWC 16GB(2x8GB) kit - https://eshop.macsales.com/item/OWC/1333DDR3S16P/

 

[flyingdoctor88]

Had that for years. Changed memory, power supply, graphics card went bust on its own. All tricks with NVRAM etc. to no avail. However, since I run a piece of software called "Macs Fan Control" AND since I set min rpm of the cpu fan to 1200: Not a single reboot in half a year! This little piece of freeware did the job. Otherwise: Still a great machine.